. The major function of this Core (RRC-D) is to support the research of the two intervention studies in this OAIC, as well as that of pilot studies supported by the OAIC. A second important function of RRC-D is to train young investigators in geriatrics and gerontology who are interested in research relevant to maintenance of functional independence of the elderly, in the performance of the procedures available within the RRC-D and in the use of stable isotope tracers in substrate turnover studies. To the extent that the investigators' time and the resources of the RRC- D permit, the RRC-D will also support other pilot and preliminary studies as well as funded studies in geriatrics and gerontology. In addition, the plan is to make the facilities and equipment of RRC-D available to young investigators in geriatrics and gerontology doing research relevant to maintenance of functional independence of the elderly. Use of the Core will be prioritized on the basis of the relevance of the research to the goal of this OAIC, which is to find effective means of preventing and reversing physical frailty and maintaining functional independence of the elderly. The specific functions of RRC-D are: a) to perform the body composition and bone quantity and quality determinations; b) to perform oral glucose tolerance tests with measurement of plasma insulin response, and obtaining blood samples for plasma lipid and lipoprotein assays; c) to perform whole body and muscle protein kinetics studies; d) to train young investigators in geriatrics and gerontology who are interested in research relevant to maintenance of functional independence of the elderly, in the performance of the above procedures and in the use of stable isotope tracers in the performance of substrate turnover studies. Performing these procedures in this Core instead of in each of the intervention studies is intended to increase efficiency by eliminating the need to have personnel trained in the performance of the procedures in these studies, and by eliminating the need to duplicate equipment. Furthermore, having all the assays performed by the same team is to enhance data quality by decreasing data variability.